1. Field Of The Invention
The present invention relates to a method for the preparation of certain substituted cinnoline derivatives, to new chemical intermediates used to prepare such cinnoline derivatives and to a method for the preparation of said intermediates. The substituted cinnoline derivatives have utility in regulating the fertility of certain plants.
2. Description Of The Background
Cross-breeding of plants has been commercially used for decades to alter the genetic make-up of plants. For successful cross-breeding, it is necessary to prevent the occurrence of self-pollination. In plants such as corn, self-pollination is prevented through mechanical means, as by removing the tassel which is the male portion of the plant and thus its pollen source. However, in other plants, such as wheat, the physiology of the plant prevents mechanical means from being successfully used to prevent self-pollination. In such plants, the male part is inaccessibly located in close proximity to the female part, making the use of mechanical intervention impractical.
Prevention of self-pollination in plants such as wheat requires a chemical means to suppress the formation of active pollen. Certain chemical pollen suppressants have already been suggested in the art, as discussed, for example, in U.S. Pat. Nos. 4,561,881, 4,604,134, 4,729,782, and 4,756,740 and the references discussed therein. Such pollen suppressants chemically inhibit the formation of pollen or induce the plant to produce non-functioning pollen. More recently, it has been discovered that certain 5-oxy or 5-amino substituted 1,4-dihydro-4-oxo-cinnoline-3-carboxylic acids and esters and salts thereof have superior pollen suppression activity, as disclosed in U.S. Pat. application Ser. No. 243,895, filed Sep. 13, 1988. The chemical pollen suppressants of that application are species of compounds having the formula: ##STR3## wherein X represents a group of the formula OR.sub.1 or NR.sub.1 R.sub.2 wherein R.sub.1 represents a C.sub.1 -C.sub.4 alkyl (optionally substituted with a C.sub.1 -C.sub.4 alkoxy group, 1 to 3 halogen atoms, or a carboxy or C.sub.1 -C.sub.4 alkoxycarbonyl group), a C.sub.2 -C.sub.4 alkenyl (optionally substituted with 1 to 3 halogen atoms), or a C.sub.2 -C.sub.4 alkynyl group and R.sub.2 represents H or CH.sub.3, with the proviso that when R.sub.1 is CH.sub.3, R.sub.2 is CH.sub.3 ;
Y is hydrogen, C.sub.1 -C.sub.22 linear alkyl or alkenyl containing up to four carbon-carbon double bonds, C.sub.3 -C.sub.6 branched alkyl or alkenyl, C.sub.1 -C.sub.4 alkoxyalkyl, -cyclohexylmethyl, halogenated C.sub.1 -C.sub.4 alkyl, phenyl, benzyl, --(CH.sub.2 CH.sub.2 O).sub.m CH.sub.2 CH.sub.3 in which m is an integer from 1 to 5, or --CH(CH.sub.2 OR.sub.4)CH.sub.2 OR.sub.5 or --CH.sub.2 CHOR.sub.4 CH.sub.2 OR.sub.5 in which either R.sub.4 or R.sub.5 but not both represent a C.sub.1 -C.sub.22 linear alkyl- or alkenylcarbonyl group containing up to four carbon-carbon double bonds and the other of R.sub.4 or R.sub.5 is H; and
R represents C.sub.1 -C.sub.4 alkyl, phenyl, naphthyl, or phenyl or naphthyl substituted with one to three substituents selected from the group consisting of halogen, CONH.sub.2, C.sub.1 -C.sub.4 alkyl or haloalkyl, C.sub.1 -C.sub.4 alkoxy or haloalkoxy, and cyano;
and salts thereof.
Unfortunately, the chemical pollen suppressants disclosed in the aforementioned application are somewhat difficult to prepare and require the use of expensive starting materials. In particular, the compounds disclosed in that application have typically been synthesized by reacting difluorobenzoyl chloride and derivatives thereof with acetonides. The difluorobenzoyl chloride and its derivatives have the formula: ##STR4## wherein R.sub.3 and n have the previously defined meanings, and the acetonides have the formula: ##STR5##
Fluorinated compounds such as those of the foregoing Formula II are very expensive raw materials as are the acetonides of Formula III and the solvents (such as DMAP) in which these compounds are normally reacted. Thus, while synthesis of compounds of Formula I was possible in the laboratory, commerical production in large scale was economically unfeasible.
It is apparent that a need exists for a procedure for synthesizing compounds of Formula I which does not require the use of expensive or difficult-to-obtain starting materials and solvents. Heretofore, that need has not been satisfied by any of the known synthesis routes for manufacturing such compounds.